Field of Invention
The present invention relates generally to measuring an analyte in a medium of a living animal using a system including a sensor implanted or inserted into the living animal. Specifically, the present invention relates to a sensor that utilizes one or more therapeutic agents, which may be incorporated within a drug eluting polymer matrix, an analyte indicator, and/or a membrane covering at least a portion of the analyte indicator.
Discussion of the Background
A sensor may be implanted within a living animal (e.g., a human) and used to measure an analyte (e.g., glucose, oxygen, cardiac markers, low-density lipoprotein (LDL), high-density lipoprotein (HDL), or triglycerides) in a medium (e.g., interstitial fluid (ISF), blood, or intraperitoneal fluid) within the living animal. The sensor may include a light source (e.g., a light-emitting diode (LED) or other light emitting element), indicator molecules, and a photodetector (e.g., a photodiode, phototransistor, photoresistor or other photosensitive element). Examples of implantable sensors employing indicator molecules to measure an analyte are described in U.S. Pat. Nos. 5,517,313 and 5,512,246, which are incorporated herein by reference in their entirety.
A sensor may include an analyte indicator, which may be in the form of indicator molecules embedded in a graft (i.e., layer or matrix). For example, in an implantable fluorescence-based glucose sensor, fluorescent indicator molecules may reversibly bind glucose and, when irradiated with excitation light (e.g., light having a wavelength of approximately 378 nm), emit an amount of light (e.g., light in the range of 400 to 500 nm) that depends on whether glucose is bound to the indicator molecule.
If a sensor is implanted in the body of a living animal, the animal's immune system may begin to attack the sensor. For instance, if a sensor is implanted in a human, white blood cells may attack the sensor as a foreign body, and, in the initial immune system onslaught, neutrophils may be the primary white blood cells attacking the sensor. The defense mechanism of neutrophils includes the release of highly caustic substances known as reactive oxygen species. The reactive oxygen species include, for example, hydrogen peroxide.
Hydrogen peroxide and other reactive oxygen species may degrade the indicator molecules of an analyte indicator. For instance, in indicator molecules having a boronate group, hydrogen peroxide may degrade the indicator molecules by oxidizing the boronate group, thus disabling the ability of the indicator molecule to bind glucose.
Glucocorticoids are used with cardiac pace makers and eye surgery to reduce inflammation. For instance, the following European patent application publications describe pace-maker leads and controlled release of steroids: EP2416783 A1 (“Improved glucocorticoid therapy”), EP1477187 B1 (“Formulation for controlled release of drugs by combining hydrophilic and hydrophobic agents”), EP1637164 A2 (“Improved formulation for controlled release of drugs by combining hydrophilic and hydrophobic agents”), and EP2303227 A2 (“Controlled release corticosteroid compositions and methods for the treatment of optic disorders”). However, these devices do not have analyte indicators, and the glucocorticoid is not used to reduce degradation of an analyte indicator. Instead, the glucocorticoid is used to stop scar tissue from building up.
There is presently a need in the art for improvements in reducing analyte indicator degradation.